Device for use in orthopaedic surgery

ABSTRACT

A device for use in orthopaedic surgery. The device includes a metallic central member. The device also includes an outer portion comprising a polymer. The outer portion surrounds the metallic central member. The outer portion has a profiled outer surface for removing bone. A surgical instrument kit including a plurality of differently sized devices of the kind described herein. The device can be a broach or rasp. A method of removing bone during orthopaedic surgery.

FIELD OF THE INVENTION

This invention relates to a device for use in orthopaedic surgery. Thisinvention also relates to a kit including a plurality of the devices.This invention further relates to a method of removing bone duringorthopaedic surgery.

BACKGROUND OF THE INVENTION

Orthopaedic surgery often involves the installation of an implant. Oneexample of such a procedure is the installation of a femoral implant inwhich the femoral head is replaced with a metallic implant having a balland a stem that extends into the medullary canal of the femur forsecuring the implant. This procedure involves cutting through thefemoral neck to remove the head and to obtain access to the medullarycanal. After the cut through the femoral neck has been made, a broach orrasp is used to remove bone that has been exposed by the cut, in orderto clear an opening to the medullary canal and to prepare the medullarycanal itself so that the femoral implant can be installed.

Normally, the broach or rasp that is used to remove the bone comprisesan elongate metallic body having a tip at one end and an outer surfacethat includes features such as ridges or teeth. The ridges or teeth canbe engaged with the bone to be removed while the broach or rasp is movedback and forth, thereby to scrape the bone away. The tip of the devicecan be used as a pick, to chip bone away. These kinds of metallic broachor rasp comprise a monolithic metallic body. A disadvantage associatedwith broaches or rasps of this kind is that they are expensive tomanufacture. Another disadvantage is that they are typically very heavy,which can make them difficult for a surgeon to manipulate effectivelyduring a surgical procedure. On the other hand, the fact that the broachor rasp comprises a solid metal body does mean that the broach or raspis particularly rigid.

In order to reduce the weight and cost associated with the metallicbroaches and rasps described above, it has been proposed to manufacturedevices using alternative materials. In particular, it has been proposedthat instead of metal, a polymer may be used. One example of this isdescribed in U.S. Pat. No. 5,454,815, which describes a bone rasp havinga plastic toothed working section with teeth and cutting edges. The raspis intended to be manufactured inexpensively, making it suitable forone-time use and thereby making cleaning and sterilisation of the usedrasp unnecessary. The rasp includes a connecting section for connectingthe rasp to an impact tool. Other devices comprised entirely of apolymer have also elsewhere been proposed.

A problem with the non-metallic device described above is that it doesnot have the same rigidity as the earlier metallic devices. During asurgical procedure involving the removal of bone, a broach or rasp issubjected to a significant amount of stress as it is impacted againstthe bone. Plastic broaches or rasps are less suited for withstandingthese forces and may potentially break or fracture during the procedure.Surgeons are also known to prefer using metallic broaches because theyare rigid and do not yield when pressed against the bone to be removed.

Accordingly, there is a need for an alternative approach to reducing thecost and weight of medical devices such as broaches or rasps, in whichat least some of the sturdiness and rigidity of earlier solid metaldevices may be retained.

SUMMARY OF THE INVENTION

Aspects of the invention are set out in the accompanying independent anddependent claims. Combinations of features from the dependent claims maybe combined with features of the independent claims as appropriate andnot merely as explicitly set out in the claims.

According to an aspect of the invention, there is provided a device foruse in orthopaedic surgery. The device includes a metallic centralmember. The device also includes an outer portion comprising a polymer.The outer portion surrounds the metallic central member. The outerportion has a profiled outer surface for removing bone.

A device such as a broach or rasp having a metallic central membersurrounded by an outer portion comprising a polymer is relatively lightcompared to earlier devices comprised of solid metal. The device is alsostronger and more rigid than earlier devices formed entirely from apolymer. Accordingly, the device can more durable than known devices andcan better withstand impaction forces involved in bone removal, forexample during when preparing the medullary cavity of a patient toreceive an implant.

According to another aspect of the invention, there is provided asurgical instrument kit comprising a plurality of differently sizeddevices of the kind described above.

The provision of a kit including differently sized devices, such asbroaches or rasps, of the kind described here can conveniently allow asurgeon to select one or more appropriately sized devices for use in asurgical procedure.

According to a further aspect of the invention, there is provided amethod of removing bone during orthopaedic surgery. The method includesproviding a device comprising a metallic central member and an outerportion comprising a polymer, wherein the outer portion surrounds themetallic central member and has a profiled outer surface. The methodalso includes impacting the device to remove the bone using the profiledouter surface.

Although devices made entirely of polymer are lighter and cheaper tomanufacture, surgeons typically prefer devices such as broaches or raspsthat have the rigidity of solid metal. Embodiments of this invention canprovide a device that is both light and rigid.

The metallic central member can include one or more engagement featuresfor resisting movement of the metallic central member relative to theouter portion during impaction of the device. The engagement featuresthus add to the structural stability of the device. The engagementfeatures can take a number of forms. For example, at least some of themcan include an aperture that passes through the metallic central memberand which can be filled with the polymer of the outer portion. At leastsome of the engagement features can be ridges or grooves on an outersurface of the metallic central member. The ridges or grooves can act togrip the polymer of the outer portion during impaction of the device.The ridges or grooves can be aligned along a direction transverse to alongitudinal axis of the device, thereby the optimally withstand theforces associated with impaction of the device.

A connector can be provided at a proximal end of the device forattachment to a handle. The connector can be formed from a proximal endof the metallic central member, allowing for a robust connection to thehandle. The connector can be a male or a female connector.

Alternatively, a proximal end of the device can form handle to be heldby a surgeon during the procedure. In some embodiments, the metalliccentral member can extend into the handle, providing the device withadditional strength.

A distal end of the metallic central member can extend through the outerportion to form a tip of the device. In this way, a relatively strongtip can be provided for chipping bone away.

The metallic central member can comprise a metallic plate. Such a plate,which may include features such as the engagement portion noted above,is easy to manufacture from sheet metal by a stamping process.

The metallic central member can, for example, comprise stainless steel,titanium or aluminium.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be described hereinafter, byway of example only, with reference to the accompanying drawings inwhich like reference signs relate to like elements and in which:

FIG. 1 shows a broach in accordance with an embodiment of the invention;and

FIG. 2 shows a broach in accordance with another embodiment of theinvention.

DETAILED DESCRIPTION

Embodiments of the present invention are described in the following withreference to the accompanying drawings.

Embodiments of this invention can provide a device such as a broach orrasp for use in orthopaedic surgery. In particular, the device isintended for use in removing bone during orthopaedic surgery. Thespecific example illustrated in FIGS. 1 and 2 and described in detailbelow takes the form of a broach to be used for removing bone from theexposed section of a femoral neck following the cutting away of thefemoral head at the neck, thereby to gain access to the medullary canalof the femur. The broach is also intended for use in removing bone fromthe medullary canal itself, in order to prepare the femur for theinstallation of an appropriately sized femoral implant. It will beappreciated, however, that a device such as a broach or a rasp accordingto an embodiment of this invention may be used in alternative surgicalprocedures for removing bone in other parts of the body.

As described in more detail below, the device includes a combination ofmetal and polymer parts. A metallic central member of the deviceprovides the device with structural strength and rigidity, while theouter portion of the device, which comprises a polymer that can bemoulded around the metallic central member, allows the cutting orrasping features of the device (for example teeth, ribs or ridges) to beformed in a manner that does not add significant weight. Overall,devices according to embodiments of this invention can retain a degreeof rigidity that approximates the rigidity and sturdiness of earliersolid metal broaches or rasps while also enabling low cost and reducedweight. Accordingly, a device of the kind described herein may also be asingle-use device that can be discarded after a surgical procedure,thereby avoiding the need to clean and sterilise the device forsubsequent further use.

A first example of a device for use in orthopaedic surgery is shown inFIG. 1. The device 10 in FIG. 1 is a broach. As noted above, the broachcan be used to remove bone from the medullary canal of a femur toprepare it for the installation of a femoral implant. The outer shapeand dimensions of the broach can, as is known in the art, be chosensubstantially to match the shape and configuration of the stem of thefemoral implant that is to be inserted into the medullary canal. Asdescribed in more detail below, it is envisaged that a surgical kit caninclude a plurality of differently sized broaches of the kind shown inFIG. 1.

The device 10 includes an elongate body having a proximal end 70 and adistal end 80. The elongate body is comprised of two main structuralparts, namely a metallic central member 30 and an outer portion 20. Theouter portion 20 at least partially surrounds the metallic centralmember 30 and comprises a polymer. FIG. 1 shows a partial cut-away viewof the device 10 so that the metallic central member 30 can be seen.

The metallic central member 30 provides structural strength and rigidityfor the device 10. The outer portion 20 comprising a polymer includesfeatures such as a profiled outer surface 40 (having teeth, ribs orridges) for removing bone. The outer portion 20 can be appropriatelyshaped according to the size and configuration of the femoral implant asnoted above.

The metallic central member 30 extends between the proximal end 70 andthe distal end of the device 10. While the outer portion 20 at leastpartially surrounds the metallic central member 30, a part of themetallic central member 30 may be exposed at one or both ends of theelongate body. For example, in the present embodiment it is shown that atip 50 of the broach 10 is formed from a distal end of the metalliccentral portion 30. The tip 50 can extend through the outer portion 20to be exposed at the distal end 80 of the elongate body of the device10. Because the tip of the device 10 is likely to experience significantstructural stress during use, the provision of a metallic tip 50 of thekind shown in FIG. 1 advantageously provides additional strength for thepart of the device 10 that is likely to require it most. Additionally,the provision of a tip 50 that is itself part of the metallic centralmember 30 allows the forces exerted on the tip 50 to be transferred backthrough the device to provide tactile feedback to the surgeon.

In use, the tip 50 can protect a leading edge of the profiled outersurface 40 of the outer portion 20 during impaction into bone, furtherimproving the durability of the device 10. The tip 50 can, for example,be conical, rounded or bullet nosed. In some examples, an upper portionof the tip may overhang the leading edge.

At the proximal end 70 of the device 10, a connector 60A can beprovided. The connector 60A in this example is formed from a proximalend of the metallic central member 30. The connector 60A provides aconnection for attachment of the device 10 to a handle (not shown in thefigures) to allow the surgeon to hold and manipulate the device 10during a surgical procedure. It is noted that the provision of ametallic connector 60A as shown in FIG. 1 can advantageously provide arobust and structurally secure connection for attachment to the handle,since the connector 60A comprises metal and is not, for example, part ofthe outer portion comprising a polymer.

In the example of FIG. 1, the connector 60A is a male connector whichcan be engaged with a corresponding female connector of the handle. Itis also envisaged that the connector at the proximal end 70 of thedevice may be a female connector. An example of a device 10 including afemale connector 60B is illustrated in FIG. 2. The features of thedevice 10 in in FIG. 2 are otherwise the same as those of the device 10shown in FIG. 1.

In FIG. 2, the connector 60B is configured to receive a corresponding amale connector of a handle. In common with the male connector 60A shownin FIG. 1, the female connector 60B shown in FIG. 2 is formed from theproximal end of the metallic central member 30. In particular, anopening in the proximal end of the metallic central member 30 can beprovided. Since the opening is formed from metal, the structuralstrength and robustness of the connector 60B is likewise enhanced.

In some examples, instead of the provision of a connector 60A or 60B, itis envisaged that a proximal end 70 of the elongate body of the device10 can form an integral handle. In this way, a separate handle andconnector 60A or 60B need not be provided. In such examples, it isfurther envisaged that the metallic central member 30 can extend intothe handle, thereby further increasing the structural strength of theoverall device. The outer portion 20 can form an outer surface of thehandle and can be appropriately shaped to be held in the surgeon'shands.

The metallic central member 30 can include one or more engagementfeatures for resisting movement of the metallic central member relativeto the outer portion 20 during use of the device 10 and for transferringthe load on the profiled surface 40 to the metallic central member 30.These engagement features can take a number of forms.

In a first example, one or more apertures 32 can be provided, which passthrough the metallic central member 30. The apertures 32 can be filledwith the polymer of the outer portion 20.

In another example, the engagement features can comprise grooves 34, 36,which can be provided on an outer surface of the metallic central member30. These grooves can also receive polymer of the outer portion 20. Asshown in FIG. 1, the grooves can have a number of differentconfigurations. The grooves 34 in FIG. 1 have a curved (for example,semi-circular) profile, while the grooves 36 have a rectangular orsquare profile. It is also envisaged that instead of (or as well as)having engagement features comprising grooves, the metallic centralmember 30 can include ribs which extend into the polymer of the outerportion 20. In common with the grooves 34, 36, the ribs can have aselected profile such as the curved or rectangular profiles noted above.

Each of the engagement features described above can increase thestructural strength of the device 10 by resisting movement (for examplerotational movement) of the metallic central member 30 relative to theouter portion 20 comprising a polymer during impaction of the device 10for the removal of bone. In some examples, the orientation of thegrooves or ridges can itself be chosen optimally to resist the impactforces associated with use of the device 10. For example, it isenvisaged that the grooves or ridges 34, 36 can be aligned along adirection transverse to a longitudinal axis of the elongate body of thedevice 10.

The metallic central member 30 can comprise, for example, a metal plate.The plate can be stamped from sheet metal during manufacture. In otherexamples, the central metallic member 30 may comprise a metallic rod.The plate or rod can be provided with the engagement features describedabove using an appropriate conventional stamping or machining process.The cross sectional shape of the metallic central member 30 can besubstantially flat (e.g. in the case that the metallic central member 30is formed from a metal plate) or can approximate a circle or aquadrilateral (e.g. in the case that the metallic central member 30 isformed from a rod).

The features of the connector 60A, 60B and the tip 50 can be formedintegrally with the metallic central member 30. For example, thesefeatures and a central part of the metallic central member that extendsbetween them can be formed from a single piece. In alternative examples,the features of the tip 50 and/or the connector 60 can be added(attached) to the central portion of the metallic central member 30(e.g. by welding) after the central portion has itself been produced.

The metallic central member 30 can comprise stainless steel, such as asurgical grade stainless steel of the kind that is known in the art. Inother examples, titanium or aluminium can be used.

As noted above, the outer portion 20 surrounds the metallic centralmember 30 and has a profiled outer surface 40. The profiled outersurface 40 can include teeth, ribs and/or ridges that can be scrapedagainst the bone to be removed. The configuration of the teeth, ribsand/or ridges is can be conventional and will not be elaborated uponfurther herein. The outer portion 20 can be formed using a conventionalmoulding process (e.g. injection moulding) to shape the polymer around apreviously prepared metallic central member 30. The mould can be used todefine the shape, size and configuration of the device 10 including theconfiguration of the profiled surface 40. The polymer can be aninjection mouldable polymer and can be provided in some examples withother constituents such as fibres for reinforcement. The polymer can,for example, be IXEF (Polyarylamide), PAEK (Polyaryletherketone) or PEEK(Polyetheretherketone). The polymer may be chosen according to factorssuch as hardness and/or ability to withstand temperatures associatedwith autoclave sterilisation. For instance, the melting points of IXEFand PEEK are around 280° C. and 343° C., respectively, while PAEK has anoperating temperature of around 250-350° C., while typical temperaturesused in autoclave sterilisation may be around 120-140° C.

During a surgical procedure, the surgeon can select an appropriatelysized broach to be used in accordance with the dimensions of the femoralimplant. Also, as is known in the art, a surgeon may begin a boneremoval procedure using a relatively small broach or rasp andsubsequently use one or more larger devices of a similar kind as theopening in medullary canal is increased in size. Accordingly, a surgicalinstrument kit according to an embodiment of this invention can includea plurality of differently-sized devices of the kind described herein.

Accordingly, there has been described a device for use in orthopaedicsurgery. The device includes a metallic central member. The device alsoincludes an outer portion comprising a polymer. The outer portionsurrounds the metallic central member. The outer portion has a profiledouter surface for removing bone. A surgical instrument kit is alsodescribed, the kit including a plurality of differently sized devices ofthe kind described herein. The device can be a broach or rasp. A methodof removing bone during orthopaedic surgery has also been described.

Although particular embodiments of the invention have been described, itwill be appreciated that many modifications/additions and/orsubstitutions may be made within the scope of the claimed invention.

1-13. (canceled)
 14. A method of removing bone during orthopaedicsurgery, the method comprising: providing a device comprising a metalliccentral member and an outer portion comprising a polymer, wherein theouter portion surrounds the metallic central member and has a profiledouter surface; and impacting the device to remove said bone using theprofiled outer surface.
 15. The method of claim 14, wherein a distal endof the metallic central member extends through the outer portion to forma tip of the device. 16-18. (canceled)
 19. The method of claim 14,wherein the metallic central member comprises one or more engagementfeatures for resisting movement of the metallic central member relativeto the outer portion during impaction of the device.
 20. The method ofclaim 19, wherein at least one of the engagement features comprises anaperture passing through the metallic central member.
 21. The method ofclaim 19, wherein at least one of the engagement features comprises aridge or a groove on an outer surface of the metallic central member.22. The method of claim 21, wherein the ridges or grooves are alignedalong a direction transverse to a longitudinal axis of the device. 23.The method of claim 14, having a connector at a proximal end thereof forattachment to a handle.
 24. The method of claim 23, wherein a proximalend of the metallic central member forms the connector.
 25. The methodof claim 14 having a proximal end forming handle, wherein the metalliccentral member extends into the handle.
 26. The method of claim 14,wherein the metallic central member comprises a metallic plate.
 27. Themethod of claim 14, wherein the metallic central member comprisesstainless steel, titanium or aluminium.